JP5098276B2 - Manufacturing method of semiconductor device - Google Patents

Description

The present invention relates to the production how a semiconductor device, particularly relates to the production how the semiconductor device for detecting the shape of the skin surface.

  With the progress of the information society, interest in security technology is increasing. In the information society, identity authentication technology for system construction such as electronic cashing has become an important key. For this purpose, fingerprint authentication technology has attracted attention.

Particularly recently, a capacitive fingerprint sensor manufactured using an LSI has been developed because of its small size and ease of workability (see Patent Document 1).
This sensor detects a concavo-convex pattern on the skin using a feedback capacitance method by a plurality of sensors arranged two-dimensionally on an LSI chip.

  In principle, a capacitive fingerprint sensor forms a sensor electrode on a semiconductor substrate, forms a passivation film on these, detects the capacitance between the skin surface and the sensor electrode via the passivation film, and It is a sensor that detects the surface irregularity shape. The principle will be described below.

  FIG. 7 is a schematic diagram of a main part for explaining the principle of a capacitive fingerprint sensor, (A) is a schematic cross-sectional view of the main part of a semiconductor device constituting the fingerprint sensor, and (B) is a plan view of the main part of the fingerprint sensor. It is a schematic diagram.

  As shown in FIG. 7A, this capacitive fingerprint sensor includes a wiring layer 102 via an insulating layer 101 over a semiconductor substrate 100 formed of LSI or the like, and an insulating layer 103 thereon. ing.

  On the insulating layer 103, for example, a sensor electrode 104 having a rectangular planar shape is formed. The sensor electrode 104 is connected to the wiring layer 102 via a contact plug 105 in a contact hole formed in the insulating layer 103.

  On the insulating layer 103, a passivation film 106 made of, for example, SiN (silicon nitride) is formed so as to cover the sensor electrode 104, thereby constituting a sensor element. As shown in FIG. 7B, a plurality of these sensor elements are two-dimensionally arranged so that sensor electrodes 104 of adjacent sensor elements do not come into contact with each other.

  Next, the operation of the capacitive fingerprint sensor will be described. At the time of fingerprint detection, first, a fingerprint detection target finger comes into contact with the passivation film 106. When a finger touches the surface of the passivation film 106, the skin touching the passivation film 106 functions as an electrode on the sensor electrode 104, and a capacitance is formed between the sensor electrode 104 and the sensor electrode 104. This capacitance is detected by a detection unit (not shown) via the wiring layer 102. Since the fingerprint of the fingertip is formed by the unevenness of the skin, when the finger is brought into contact with the passivation film 106, the distance between the skin as the electrode and the sensor electrode 104 is the convex portion and the concave portion forming the fingerprint. It will be different.

  This difference in distance is detected as a difference in capacity. Therefore, if these different capacitance distributions are detected, it becomes the shape of the convex portion of the fingerprint. That is, this capacitive sensor can detect a fine uneven state of the skin.

By the way, in order to protect the surface of the semiconductor device including the capacitive fingerprint sensor, as described above, the passivation film 106 such as a SiN film is coated on the surface.
Recently, an organic polyimide film is used as a passivation film in order to provide a buffering property to the passivation film (see, for example, Patent Document 2).

Such a polyimide film is usually made of an amic acid-based polyimide, and is formed at a film thickness of 3000 nm and a polyimide forming temperature of about 320 ° C. to 380 ° C.
Here, in order to fully exhibit the function of the passivation film, it is desirable to increase the film thickness or to stack the passivation film in several layers and form it on the surface of the semiconductor device.
JP 2003-269907 A Japanese Patent No. 3630483

  However, in a capacitive fingerprint sensor, if the passivation film is formed thick or stacked in layers, the distance between the sensor electrode and the finger that contacts the sensor surface increases, and the sensor electrode and the sensor There is a problem that the capacitance with the surface is reduced, and the sensitivity for detecting fingerprints is extremely reduced.

In order to improve the sensitivity of the capacitive fingerprint sensor, it is desirable to shorten the distance between the sensor electrode and the finger surface. For this purpose, it is desirable to reduce the thickness of the passivation film.
Therefore, in the conventional capacitive fingerprint sensor, the film thickness of the amic acid-based polyimide resin is made as thin as possible, and the polyimide film thickness is formed to about 1000 nm. However, if the amidic acid-based polyimide resin is formed to be thinner, the strength of the film itself is lowered, so that it is difficult to reduce the film thickness beyond this.

  On the other hand, recently, an ester resin polyimide has been developed, and a polyimide resin that can be imidized at a lower temperature than an amic acid resin has appeared. Experiments have revealed that this ester-based resin polyimide has the same film thickness and slightly higher film strength than amidic acid-based polyimide. Therefore, when ester-based polyimide was used for a capacitive fingerprint sensor, the same strength was obtained up to a polyimide film thickness of 800 nm. However, when the film thickness was 800 nm or less, the reliability of the passivation film was lowered. Furthermore, since the reaction temperature of the imide is lower than that of the amic acid-based polyimide, there is a problem that the imide film cannot be formed uniformly when high temperature curing is applied at once. When heated at once, film rupture may occur partially. Originally, ester-based polyimide was developed so as to undergo a crosslinking reaction at a low temperature, and thus is outside the range of use or guaranteed for a method of forming at a high temperature of 320 ° C. or higher.

  That is, when an amic acid-based polyimide is used, if it is formed with a thickness of 1000 nm or less, there arises a problem that a film strength that can withstand friction with a finger cannot be obtained sufficiently. On the other hand, when an ester-based polyimide is used, if it is formed at 800 nm or less, a film strength that can withstand friction with a finger cannot be obtained sufficiently, and if a high-temperature cure is used, an imide film cannot be formed uniformly. . Therefore, the polyimide film thickness could not be formed to 800 nm or less.

  In order to solve these problems, how to realize a semiconductor device with sufficient sensitivity and strength by forming an ultra-thin polyimide film of 800 nm or less on the surface of a capacitive fingerprint sensor semiconductor device. The issue is whether to do this.

The present invention has been made in view of these points, with the following polyimide film 800nm as the passivation film, and an object thereof is to provide a manufacturing how a semiconductor device having a sufficient sensitivity and strength, etc. .

According to an aspect of the present invention , in a method of manufacturing a semiconductor device that detects a capacitance between a skin surface and a sensor electrode via an insulating layer and detects a shape of the skin surface, the sensor electrode includes silicon oxide. Forming a first insulating film; forming a second insulating film containing silicon nitride on the first insulating film; and a third insulating film containing polyimide on the second insulating film. Forming the third insulating film, wherein the insulating layer includes the first insulating film, the second insulating film, and the third insulating film. includes the step of heating and curing the said third insulating film, the third insulating film, the formed on the uppermost layer of the semiconductor device manufacturing method having a thickness of the semiconductor device is 400nm or more 700nm or less Is provided.

In such a method for manufacturing a semiconductor device, in the method for manufacturing a semiconductor device in which the capacitance between the skin surface and the sensor electrode is detected via an insulating layer and the shape of the skin surface is detected, the film thickness is formed on the uppermost layer of the semiconductor device. An insulating film having a thickness of 400 nm to 700 nm is formed.

With the disclosed technology , a method for manufacturing a semiconductor device and a semiconductor device with sufficient sensitivity and strength can be realized.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First, the basic principle of a method for manufacturing a passivation film formed on the uppermost layer of a semiconductor device constituting a capacitive fingerprint sensor will be described.

FIG. 1 is a diagram illustrating a flow of a method for manufacturing a passivation film.
First, an insulating film that is a first passivation film, for example, a silicon nitride film is formed on the upper layer of the semiconductor device that constitutes the sensor electrode, and then an insulating film that is a second passivation film is formed on the SiN film. Photosensitive polyimide is applied (step S1). Subsequently, pre-baking of the non-photosensitive polyimide film is performed (step S2). Next, in order to perform patterning of the non-photosensitive polyimide film, a resist is applied on the non-photosensitive polyimide film (step S3). Subsequently, the resist layer is baked (step S4). Next, the resist layer is exposed (step S5). Next, the resist layer is developed, and the resist layer is removed from the non-photosensitive polyimide film (step S6). Here, after the resist layer is removed from the non-photosensitive polyimide film, a pattern is formed on the non-photosensitive polyimide film.

  Then, after drying the patterned non-photosensitive polyimide film, the non-photosensitive polyimide film is pre-cured at a predetermined temperature and atmosphere (step S7). Subsequently, the non-photosensitive polyimide film is cured and cured at a predetermined temperature and atmosphere (step S8). Finally, post-processing is performed to further cure the non-photosensitive polyimide film (step S9). Finally, a non-photosensitive polyimide film having a film thickness of 400 nm to 700 nm is formed on the uppermost layer of the semiconductor device (step S10).

By such a flow, a passivation film made of an extremely thin non-photosensitive polyimide film can be formed on the uppermost layer of the semiconductor device constituting the capacitive fingerprint sensor.
When photosensitive polyimide is used instead of non-photosensitive polyimide, Step S3, Step S4, and Step S6 are omitted from the above flow, and the photosensitive polyimide is directly exposed in Step S5. As a result, a passivation film made of a photosensitive polyimide film can be formed on the uppermost layer of the semiconductor device by directly exposing and patterning the photosensitive polyimide. The polyimide material is, for example, ester-based polyimide.

  Thus, in the method of manufacturing a semiconductor device constituting a capacitive fingerprint sensor, the capacitance between the skin surface and the conductive film is detected through the insulating layer of the SiN film and the polyimide film as the passivation film, and the semiconductor device A polyimide film having a thickness of 400 nm to 700 nm or less is formed on the uppermost layer.

  According to such a passivation film manufacturing method, the polyimide film, which is the passivation film formed in the uppermost layer, is formed with a very thin film thickness, so that it is provided in a semiconductor device constituting a capacitive fingerprint sensor. The distance from the sensor electrode to the finger skin surface can be further shortened. As a result, the capacitance between the sensor electrode and the skin surface through the passivation film can be increased, and the sensitivity when detecting the uneven shape of the fingerprint can be improved.

  Even if the polyimide film is formed to be extremely thin, the polyimide film has sufficient mechanical strength, so that the reliability of the semiconductor device can be equal to or improved from the conventional product.

  Furthermore, by making the film thickness of the polyimide film extremely thin, the distance between the ESD (Electro Static Discharge) hole (described later) and the polyimide film surface is further shortened. Therefore, the charge charged (charged up) on the polyimide film surface is likely to diffuse into the ESD hole portion. As a result, the influence of charging on the capacitance between the sensor electrode and the skin surface can be reduced, and the sensitivity of the capacitive fingerprint sensor can be further improved.

  Here, the polyimide film may be formed to 400 nm or less, and the fingerprint detection rate may be further improved. However, if the polyimide film is thinned to 400 nm or less, the effect as a buffer material is further reduced, and the film strength of the polyimide film is increased. Is further reduced, and sufficient reliability guarantee (such as polyimide damage caused by rubbing with a finger) cannot be obtained. Therefore, it is preferable to form the polyimide film with a thickness of 400 nm or more.

  Next, a specific method for manufacturing a passivation film formed on the uppermost layer of the semiconductor device constituting the capacitive fingerprint sensor will be described. In this embodiment, a specific method for manufacturing a passivation film formed on the uppermost layer of a semiconductor device constituting a capacitive fingerprint sensor will be described by taking a semiconductor device having a CMOS (Complementary Metal Oxide Semiconductor) transistor as an example. .

FIG. 2 is a schematic cross-sectional view of an essential part of a semiconductor device manufacturing process.
This figure is an example of a semiconductor device on which a CMOS transistor is mounted, and schematically shows a main part of the semiconductor device constituting a capacitive fingerprint sensor.

First, an outline of a configuration in which a silicon nitride film, which is a passivation film, is formed on the upper layer of a semiconductor device constituting a capacitive fingerprint sensor will be described.
In the semiconductor device, for example, an element isolation region 11 that defines an element region is formed on a Si (silicon) substrate 10. A well 12 is formed in the Si substrate 10, and a gate electrode 14 is formed on the well 12 via a gate insulating film 13.

  An insulating layer 15 that is a sidewall is formed on the side surface of the gate electrode 14. Source / drain regions 16 are formed on both sides of the gate electrode 14 on which the insulating layer 15 is formed.

As described above, a plurality of MOS transistors 17 constituting a CMOS are provided on the Si substrate 10.
A 200 nm thick SiON (silicon oxynitride) film 18 is formed on the Si substrate 10. Further, a TEOS (Tetra Ethyl Ortho Silicate) -NSG (Non-doped Silicate Glass) film 19 having a film thickness of 800 nm, which is an interlayer insulating film, is formed on the SiON film 18.

  Then, a W (tungsten) layer 20 as a bulk contact penetrates the SiON film 18 and the TEOS-NSG film 19 and is electrically connected to the source / drain region 16 or the gate electrode 14. Further, the W layer 20 is electrically connected to a first Al (aluminum) wiring layer 21 patterned on the TEOS-NSG film 19.

  On the Al wiring layer 21, a TEOS-NSG film 30 having a thickness of 1200 nm, which is an interlayer insulating film, is formed. A TEOS-NSG film 31 having a thickness of 100 nm is further formed on the TEOS-NSG film 30.

  From the Al wiring layer 21, a W layer 32 as a bulk contact is formed so as to penetrate the TEOS-NSG film 30 and the TEOS-NSG film 31, and the W layer 32 is patterned on the TEOS-NSG film 31. The second Al wiring layer 33 is electrically connected.

  A TEOS-NSG film 40 having a thickness of 400 nm is formed on the second Al wiring layer 33. On the TEOS-NSG film 40, an SOG (Spin On Glass) film 41 having a thickness of 500 nm is formed. A TEOS-NSG film 42 having a thickness of 300 nm is formed on the SOG film 41.

  Then, on the SOG film 41 and the TEOS-NSG film 42, TiN (titanium nitride) films 43a and 43b having a film thickness of 200 nm are patterned. Here, the TiN film 43a is a sensor electrode of a semiconductor device constituting a capacitive fingerprint sensor, and is formed such that the length in the longitudinal direction of the TiN film 43a when viewed from above the semiconductor device is 50 μm. ing. The TiN film 43b is grounded to prevent ESD due to charging of the polyimide film surface described later. The TiN films 43 a and 43 b are electrically connected via the second Al wiring layer 33 and the TiN layer 44.

  Further, a TEOS-NSG film 50 having a thickness of 100 nm is formed on the TiN films 43a and 43b. A SiN film 51 having a thickness of 700 nm, which is a first passivation film, is formed on the TEOS-NSG film 50. Here, the SiN film 51 on the pad portion 52 of the semiconductor device is deeply etched. The first passivation film may be an oxynitride film such as a SiON film in addition to a nitride film such as a SiN film. This first passivation film becomes the base of a second passivation film described later.

Thus, in this step, an integrated circuit is formed on the Si substrate 10, and multilayer wiring layers such as the W layers 20, 32 and the Al wiring layers 21, 33 are formed.
The multilayer wiring layer constitutes a plurality of wirings connected to a plurality of elements such as the MOS transistor 17, and is further electrically connected to the TiN film 43a which is a sensor electrode to constitute a sensor circuit and the like. A plurality of interlayer insulating films are formed between the multilayer wiring layers, and the uppermost layer is covered with the SiN film 51.

FIG. 3 is a schematic cross-sectional view of an essential part of a semiconductor device manufacturing process.
After the SiN film 51 is formed on the TEOS-NSG film 50, a resist 60 is applied. Then, exposure and development are performed, and the resist 60 is patterned.

  Using the patterned resist 60 as a mask, the TEOS-NSG film on the ESD hole portion 53 and the pad portion 52 is etched (not shown), and each of the TiN film 43b in the ESD hole portion 53 and the Al wiring layer 33 in the pad portion 52 is etched. To expose the surface.

Thereafter, the resist 60 is dehydrated in a N ₂ (nitrogen) atmosphere at 430 ° C. for 30 minutes in a thermal furnace.
FIG. 4 is a schematic cross-sectional view of an essential part of a semiconductor device manufacturing process.

  After removing the resist 60 formed in the previous step, an ester-based non-photosensitive polyimide serving as a second passivation film is applied so as to have a film thickness of 700 nm, for example (not shown), and is applied to the SiN film 51. A non-photosensitive polyimide film 61 is formed. Then, the non-photosensitive polyimide film 61 is pre-baked at 120 to 150 ° C. for 120 seconds. Further, a resist is applied thereon (not shown). Then, the resist is baked. Then, an exposure process is performed, and the resist and the non-photosensitive polyimide film 61 are simultaneously patterned. Then, using a rinsing liquid, only the resist is removed (not shown). Here, the non-photosensitive polyimide film 61 is patterned on the SiN film 51 so as to open the pad portion 52 and the ESD hole portion 53 by exposure. In particular, regarding the opening of the ESD hole portion 53, the non-photosensitive polyimide film 61 is formed so as to open wider than the area of the upper surface of the TiN film 43b. Specifically, when the area of the upper surface of the TiN film 43b is 6 μm × 6 μm, the non-photosensitive polyimide film 61 is formed so as to open wider than this area. More specifically, the non-photosensitive polyimide film 61 is formed so that the opening diameter in the ESD hole portion is larger than the ESD hole diameter and not more than 50 μm.

In this manner, the non-photosensitive polyimide film 61 is formed up to the end of the ESD hole portion 53. Thereafter, the non-photosensitive polyimide film 61 is dried for a while.
Subsequently, in order to previously dehydrate excess water from the non-photosensitive polyimide film 61, the non-photosensitive polyimide film 61 is preheated. Specifically, the temperature of the non-photosensitive polyimide film 61 is set to 190 in an atmosphere of N ₂ gas, inert gas (Ar (argon), CO ₂ (carbon dioxide)) or a mixed gas thereof. The temperature is set to ℃ to 240 ℃, and precure is performed for 60 seconds to 240 seconds. The reason for setting the temperature of the non-photosensitive polyimide film 61 to 190 ° C. to 240 ° C. is that cross-linking within the molecule of the non-photosensitive polyimide is liable to occur at 240 ° C. or higher. This is because dehydration does not occur.

Here, the precure is performed in an atmosphere of N ₂ gas, inert gas, or a mixed gas thereof. Thereby, the phenomenon that only a part of the non-photosensitive polyimide film 61 is cured can be avoided.

Subsequently, N ₂ gas, inert gas, or a mixed gas thereof is introduced into the processing chamber so that the flow rate becomes 110 liters / min or more, and the processing chamber is filled with N ₂ gas, inert gas, or a mixed gas thereof. Let Then, a semiconductor device is installed in the processing chamber (not shown). Then, in order to cure the non-photosensitive polyimide film 61, the non-photosensitive polyimide film 61 is set to 350 ° C. to 380 ° C., and curing is performed for 40 minutes in an N ₂ gas, an inert gas, or a mixed gas atmosphere thereof. . After curing, the film thickness of the non-photosensitive polyimide film 61 is decreased from 700 nm to 500 nm (not shown).

Here, when the curing temperature is set to 400 ° C. or higher, the Al wiring layers 21 and 33 are deformed. Moreover, in the case of ester-type polyimide resin, it hardens | cures even at about 250 degreeC. However, in order to further promote the internal dehydration treatment and film strength, it is preferable to cure at 350 ° C. or higher. Furthermore, by curing in an atmosphere of N ₂ gas, inert gas, or a mixed gas thereof, intramolecular crosslinking is promoted, and a non-photosensitive polyimide film 61 having sufficient film strength can be formed. .

In order to further improve the moisture absorption resistance of the non-photosensitive polyimide film 61, the curing is started within 120 minutes immediately after the pre-curing process. However, if the semiconductor device patterned with the non-photosensitive polyimide film 61 is left in the N ₂ gas atmosphere without being exposed to the air, the non-photosensitive polyimide film 61 is cured after being left for 120 minutes or more. May be. For example, the semiconductor device may be stored for 120 minutes or more in a container filled with N ₂ gas and then cured. This is because if there is an N ₂ gas atmosphere, there is no moisture in the atmosphere, and moisture is not absorbed by the non-photosensitive polyimide film 61.

  Subsequently, post-processing is performed in order to remove foreign substances adhering to the surface of the non-photosensitive polyimide film 61. In this post-treatment, the surface of the non-photosensitive polyimide film 61 is removed to such an extent that the non-photosensitive polyimide film 61 is not damaged. Specifically, the surface of the non-photosensitive polyimide film 61 is ashed so that the film thickness of the non-photosensitive polyimide film 61 is reduced by 45 nm to 55 nm (not shown).

The ashing process is performed by, for example, oxygen plasma in which the temperature of the non-photosensitive polyimide film 61 is set to 25 ° C. to 50 ° C., the O ₂ (oxygen) gas flow rate is 600 sccm, and the discharge power is 600 W to 800 W.

  Then, after the ashing process, a non-photosensitive polyimide film 61 having a final film thickness of 450 nm is formed. The final film thickness of the non-photosensitive polyimide film 61 need not be limited to 450 nm, and the film thickness of the non-photosensitive polyimide film 61 to be finally formed is adjusted by adjusting the film thickness in the above coating process. What is necessary is just to exist in the range of 400 nm-700 nm.

  In the case of using photosensitive polyimide instead of non-photosensitive polyimide, resist coating, resist baking, resist exposure and resist removal are omitted from the above steps, and the photosensitive polyimide is directly patterned. As a result, a passivation film made of a photosensitive polyimide film can be formed on the uppermost layer of the semiconductor device. The polyimide material is, for example, ester-based polyimide.

  When a finger is brought into contact with the surface of a capacitive fingerprint sensor composed of such a semiconductor device, the capacitance between the TiN film 43a through the passivation film and the finger skin surface is detected by the TiN film 43a as a sensor electrode. The uneven shape of the finger skin surface is detected.

  Thus, in the method of manufacturing a semiconductor device constituting a capacitive fingerprint sensor, the capacitance between the skin surface and the conductive film is detected through the insulating layer of the SiN film and the polyimide film as the passivation film, and the semiconductor device A polyimide film having a thickness of 400 nm to 700 nm or less is formed on the uppermost layer.

  According to such a passivation film manufacturing method, the polyimide film, which is the passivation film formed in the uppermost layer, is formed with a very thin film thickness, so that it is provided in a semiconductor device constituting a capacitive fingerprint sensor. The distance from the sensor electrode to the finger skin surface can be further shortened. As a result, the capacitance between the sensor electrode and the skin surface through the passivation film can be increased, and the sensitivity when detecting the uneven shape of the fingerprint can be improved.

  Even if the polyimide film is formed extremely thin, the polyimide film is sufficiently cured and post-processed. Therefore, the polyimide film has excellent moisture absorption resistance and sufficient mechanical strength, so that the reliability of the semiconductor device About the property, it becomes equivalent to a conventional product, or can be improved from a conventional product.

  In addition, the distance between the ESD hole portion and the polyimide film surface is further shortened by making the film thickness of the polyimide film extremely thin. Therefore, the charge charged on the surface of the polyimide film easily diffuses into the ESD hole portion. As a result, the influence of charging on the capacitance between the sensor electrode and the skin surface can be reduced, and the sensitivity of the capacitive fingerprint sensor can be further improved.

Furthermore, by reducing the film thickness of the polyimide film, the uneven step between the polyimide film and the ESD hole portion is reduced, and the slip characteristic of the surface of the capacitive fingerprint sensor is improved.
Further, since the polyimide film is formed up to the vicinity of the end of the ESD hole portion, the passivation effect of the polyimide film is further increased.

  Next, the effect of forming a very thin polyimide film, which is a passivation film of a semiconductor device constituting a capacitive fingerprint sensor, will be described. Here, in order to confirm the effect, a semiconductor device in which polyimide films having three kinds of film thickness were formed was manufactured.

  As a semiconductor device constituting a capacitive fingerprint sensor, a fingerprint sensor A having a polyimide film with a film thickness of 2000 nm, a fingerprint sensor B having a polyimide film with a film thickness of 800 nm, and a film thickness ranging from 400 nm to 700 nm As an example of the polyimide film, three types of semiconductor devices of the fingerprint sensor C on which a 450 nm polyimide film was formed were manufactured.

FIG. 5 is a diagram for explaining a fingerprint image read by a capacitive fingerprint sensor.
As can be seen from this image, the contrast of the fingerprint image of the fingerprint sensor A is the lowest, and then the contrast increases in the order of the fingerprint sensor B and the fingerprint sensor C. In particular, in the fingerprint sensor C, the shade reflecting the unevenness of the fingerprint is clear, and it seems that the authenticity is further improved.

  Also, the fingerprint matching rates of fingerprint sensor A, fingerprint sensor B, and fingerprint sensor C were examined. Here, the matching rate is, for example, when a capacitive fingerprint sensor can store 100 dot patterns (a dot pattern is stored as 0 or 1. Here, 0 is a portion where there is no fingerprint. The white part of the image is reflected, and 1 is the skin part, and the black part of the image is reflected.) Once the finger is brought into contact with the capacitive fingerprint sensor, the dot pattern of the fingerprint is stored in the semiconductor device. Then, the finger is again brought into contact with the capacitive fingerprint sensor to obtain a fingerprint dot pattern, and the rate of how much the dot pattern matches the previous dot pattern.

For example, if there are 80 matched dots in 100 dot patterns, the matching rate is 80.0%.
The matching rate results were 30.3%, 56.3%, and 87.9% in the order of fingerprint sensor A, fingerprint sensor B, and fingerprint sensor C, respectively.

Thus, it has been found that by reducing the thickness of the polyimide film, the contrast of the fingerprint image is improved and the matching rate is also improved.
In fingerprint sensor C, HAST (Highly Accelerated Temperature and Humidity Stress Test) 1KH test, which is a highly accelerated life test, and UHAST (Unbiased Highly Accelerated temperature and humidity), which is a highly accelerated life test with no bias applied to the device. Stress Test) As a result of the 336H test, no defective fingerprint sensor was generated for the semiconductor device C.

In addition, when the photosensitive polyimide film 450 nm was formed as the passivation film of the fingerprint sensor C, the same result as that obtained when the non-photosensitive polyimide film 450 nm was formed was obtained.
Next, the strength of the polyimide film when the polyimide film was formed extremely thin was confirmed. Here, in order to confirm the effect, two types of polyimide films were formed on a silicon wafer substrate, and the stress of each polyimide film was measured by a tape test and a warp measuring device.

FIG. 6 is a diagram for explaining the strength of the polyimide film.
Two types of samples, sample D and sample E, were prepared. Sample D is a non-photosensitive polyimide film formed on a silicon wafer substrate having a SiN film on the surface so as to have a thickness of 1000 nm. On the other hand, Sample E is an example of a polyimide film having a film thickness in the range of 400 nm to 700 nm, in which a photosensitive polyimide film is formed on a silicon wafer substrate having a SiN film on the surface so as to have a thickness of 500 nm. Here, as the material of the polyimide film of sample E, photosensitive polyimide of ester resin is used. The curing temperature was both in the range of 230 ° C to 380 ° C. About the pre-cure and the post-treatment, both the sample D and the sample E were performed under the same conditions as the above-mentioned examples.

  First, as for the tape test, in sample D, the polyimide film was not peeled from the sample cured at 260 ° C. to 380 ° C. On the other hand, in sample E, no peeling occurred at the interface between the polyimide film and the substrate for the sample cured at 230 ° C. to 380 ° C.

In particular, it was found that, even when the sample E was cured at a lower temperature than the sample D, a polyimide film that did not peel was obtained.
Next, when measuring the stress in the film from the warpage measuring device, in sample D, the cure temperature is 21 MPa when the cure temperature is 230 ° C., 27 MPa when the cure temperature is 290 ° C., and 38 MPa when the cure temperature is 380 ° C. Sample E was 32 MPa when the cure temperature was 230 ° C, 39 MPa when the cure temperature was 290 ° C, and 48 MPa when the cure temperature was 380 ° C.

  Accordingly, it was found that the sample E has a relatively high stress even when cured at a lower curing temperature. That is, it was found that a stronger film was formed in sample E than in sample D.

When the non-photosensitive polyimide film 500 nm of the ester resin was formed on the silicon wafer substrate, the result was the same as that of the sample E.
Thus, it has been found that sufficient mechanical strength can be obtained even when a passivation film is formed on the uppermost layer of a semiconductor device constituting a capacitive fingerprint sensor.

  Note that what is detected by the above sensor is not limited to fingerprints. For example, the skin surface of the palm can be easily detected by increasing the number of semiconductor devices shown in FIG. 4 and increasing the sensor area.

  (Supplementary Note 1) In the method of manufacturing a semiconductor device, in which the capacitance between the skin surface and the conductive film is detected through an insulating layer, and the shape of the skin surface is detected, the film thickness is 400 nm to 700 nm on the uppermost layer of the semiconductor device. A method for manufacturing a semiconductor device, comprising: forming an insulating film.

(Additional remark 2) The manufacturing method of the semiconductor device of Additional remark 1 characterized by the material of the said insulating film being ester-type polyimide.
(Additional remark 3) In the case of forming the said insulating film, the temperature which hardens the said insulating film is 350 degreeC or more and 380 degrees C or less, The manufacturing method of the semiconductor device of Additional remark 1 or 2 characterized by the above-mentioned.

  (Additional remark 4) When hardening the said insulating film, nitrogen gas or an inert gas or the mixed gas of the said nitrogen gas and the said inert gas is flowed in 110 liter / min or more, and the atmosphere of the said nitrogen gas or the said inert gas The method for manufacturing a semiconductor device according to any one of appendices 1 to 3, wherein the insulating film is hardened in the inside.

  (Additional remark 5) Before hardening the said insulating film, the said insulating film is set to 190 degreeC or more and 240 degrees C or less, and preheating is performed for 60 seconds or more and 240 seconds or less, The additional notes 1 thru | or 4 characterized by the above-mentioned A manufacturing method of a semiconductor device given in any 1 paragraph.

  (Additional remark 6) When performing the said preheating, the said preheating is performed in the atmosphere of the said nitrogen gas, the said inert gas, or the said mixed gas, It is any one of the additional marks 1 thru | or 5 characterized by the above-mentioned. Semiconductor device manufacturing method.

(Supplementary note 7) The method for manufacturing a semiconductor device according to any one of supplementary notes 1 to 6, wherein the insulating film is cured within 120 minutes after the preliminary heating.
(Supplementary note 8) The supplementary notes 1 to 6, wherein after the preliminary heating, the semiconductor device in which the insulating film is formed is stored in a container filled with the nitrogen gas, the inert gas, or the mixed gas. The manufacturing method of the semiconductor device as described in any one of these.

  (Additional remark 9) After hardening the said insulating film, the said surface of the said insulating film is removed by the ashing process so that the film thickness of the said insulating film may be reduced to 45 nm or more and 55 nm or less, It is characterized by the above-mentioned. The method for manufacturing a semiconductor device according to any one of appendices 1 to 8.

  (Additional remark 10) The said insulating film is formed to the end of the ESD hole part arrange | positioned in the said semiconductor device, The manufacturing method of the semiconductor device as described in any one of additional remark 1 thru | or 9 characterized by the above-mentioned.

(Appendix 11) In the case of forming the insulating film, an ester-based non-photosensitive polyimide is used as the polyimide,
Applying the non-photosensitive polyimide to the surface of the semiconductor device;
A step of pre-baking the applied non-photosensitive polyimide film;
Applying a resist to the upper layer of the pre-baked non-photosensitive polyimide film;
Patterning the non-photosensitive polyimide film using the resist as a mask;
Drying the patterned non-photosensitive polyimide film and performing a pre-cure;
Curing the non-photosensitive polyimide film that has been pre-cured;
The method for manufacturing a semiconductor device according to appendix 2, wherein:

(Appendix 12) In the case of forming the insulating film, an ester-based photosensitive polyimide is used as the polyimide,
Applying the photosensitive polyimide to the surface of the semiconductor device;
A step of pre-baking the applied photosensitive polyimide film;
Patterning the pre-baked photosensitive polyimide film;
Drying the patterned photosensitive polyimide film and performing a pre-cure;
Curing the photosensitive polyimide film that has been pre-cured; and
The method for manufacturing a semiconductor device according to appendix 2, wherein:

(Supplementary note 13) The method for manufacturing a semiconductor device according to supplementary note 1 or 10, wherein a base of the insulating film is a nitride film or an oxynitride film.
(Additional remark 14) In the semiconductor device which detects the capacity | capacitance of a skin surface and an electrically conductive film through an insulating layer, and detects the shape of the said skin surface, the film thickness of the insulating film formed in the uppermost layer of the said insulating layer is 400 nm A semiconductor device having a thickness of 700 nm or less.

(Additional remark 15) The semiconductor device of Additional remark 14 characterized by the material of the said insulating film being ester-type polyimide.
(Supplementary note 16) The semiconductor device according to Supplementary note 14 or 15, wherein the insulating film is formed up to an end of an ESD hole portion where the semiconductor device is disposed.

(Supplementary note 17) The semiconductor device according to any one of supplementary notes 14 to 16, wherein a base of the insulating film is a nitride film or an oxynitride film.
(Additional remark 18) The semiconductor device as described in any one of additional remark 14 thru | or 17 whose opening diameter of the ESD hole part of the said insulating film is larger than an ESD hole diameter, and is 50 micrometers or less.

It is a figure explaining the flow of the manufacturing method of a passivation film. FIG. 3 is a schematic cross-sectional view of a relevant part of a semiconductor device manufacturing process (part 1); FIG. 6 is a schematic cross-sectional view of a relevant part of a semiconductor device manufacturing process (part 2); FIG. 6 is a schematic cross-sectional view of a relevant part of a semiconductor device manufacturing process (part 3); It is a figure explaining the fingerprint image read with the capacitive fingerprint sensor. It is a figure explaining the intensity | strength of a polyimide film. It is a principal part schematic diagram explaining the principle of a capacitive fingerprint sensor, (A) is a principal part cross-sectional schematic diagram of the semiconductor device which comprises a fingerprint sensor, (B) is a principal part schematic diagram of a fingerprint sensor. is there.

Explanation of symbols

10 Si substrate 11 Element isolation region 12 Well 13 Gate insulating film 14 Gate electrode 15 Insulating layer 16 Source / drain region 17 MOS transistor 18 SiON film 19, 30, 31, 40, 42, 50 TEOS-NSG film 20, 32 W layer 21, 33 Al wiring layer 41 SOG film 43a, 43b TiN film 44 TiN layer 51 SiN film 52 Pad part 53 ESD hole part 60 Resist 61 Non-photosensitive polyimide film

Claims (8)

In the method of manufacturing a semiconductor device for detecting the capacitance between the skin surface and the sensor electrode through the insulating layer and detecting the shape of the skin surface,
Forming a first insulating film containing silicon oxide on the sensor electrode;
Forming a second insulating film containing silicon nitride on the first insulating film;
Forming a third insulating film containing polyimide on the second insulating film;
Have
The insulating layer includes the first insulating film, the second insulating film, and the third insulating film,
The step of forming the third insulating film includes a step of heating and curing the third insulating film,
The third insulating film, the formed on the uppermost layer of the semiconductor device, a method of manufacturing a semiconductor device, wherein the film thickness is 400nm or more 700nm or less. The method according to claim 1, wherein a material of the third insulating film is an ester-based polyimide.
The method for manufacturing a semiconductor device according to claim 1, wherein the step of curing the third insulating film includes a step of heating the third insulating film to 350 ° C. or higher and 380 ° C. or lower. In the step of curing the third insulating film, nitrogen gas, an inert gas, or a mixed gas of the nitrogen gas and the inert gas is flowed in at least 110 liters / minute, and the atmosphere of the nitrogen gas or the inert gas is injected. in the third method of manufacturing a semiconductor device according to any one of claims 1 to 3, characterized in that curing the insulating film. Characterized in that it has prior to the step of curing the third insulating film, the third insulating film is set to 190 ° C. or higher 240 ° C. or less, a step of performing pre-heated in a 60 seconds 240 seconds or less than A method for manufacturing a semiconductor device according to any one of claims 1 to 4. Wherein the step of performing a pre-heating method of manufacturing a semiconductor device according to claim 5, characterized in that said pre-heated in an atmosphere of the nitrogen gas or the inert gas or the mixed gas. 7. The method of manufacturing a semiconductor device according to claim 5 , wherein the third insulating film is cured within 120 minutes after the preliminary heating step . After said third insulating film Ru cured step, the surface of the third insulating film by ashing treatment, the third step of the thickness of the insulating film is divided so as to reduce 55nm less than 45nm A method for manufacturing a semiconductor device according to claim 1, comprising:

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